A network routing link state real-time sensing method based on cross-layer cooperation

Abstract

The application relates to a network routing link state real-time sensing method based on cross-layer cooperation. Link state detection in a routing protocol not only adopts Hello packet interaction at a network layer, but also adopts frame synchronization indication reported at a physical layer. The inter-satellite link state is realized by adopting an active detection mode for the inter-satellite laser terminal frame synchronization state, real-time detection of the inter-satellite link on-off state and link quality is completed in combination with inter-satellite link signal capture tracking, signal processing, link quality detection and other functions, and the detection result is reported to an inter-satellite routing protocol processing function unit to trigger routing update. The method can effectively control routing interaction overhead, can respond in real time and perform fast re-routing when inter-satellite link on-off change, satellite node abnormal failure and other conditions occur, and provides a real-time and accurate link state detection scheme for a wireless network communication system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of satellite communication, in particular, to a network routing link state real-time sensing method based on cross-layer cooperation. BACKGROUND

[0002] Link state-based routing protocols build routing tables by collecting and exchanging link state information in the network, thereby selecting the best path. This type of protocol has higher efficiency and reliability in handling large and complex network environments. It mainly includes two types of routing protocols: OSPF (Open Shortest Path First) and IS-IS (Intermediate System to Intermediate System).

[0003] Taking OSPF as an example, OSPF is a link state routing protocol based on IGP (Interior Gateway Protocol). Link state routing protocols use the cost of reaching the destination as a metric. Routers calculate the weight value of reaching neighbors according to interface bandwidth, the higher the bandwidth, the smaller the weight value, and the better the path state. When the topology changes, the router does not send a routing table, but only sends a LSA (Link State Advertisement) containing link change information, and then each router updates the LSDB (Link State DataBase) and performs SPF (Shortest Path First) algorithm to calculate the route.

[0004] Each OSPF running router maintains a link state database LSDB for tracking network link state. The database stores various link state advertisements (LSAs) reflecting the status of routers and their links, including available interfaces, known reachable routes, and link state information. The link state database is actually a complete network topology map of the region, which is the basis for the router to establish a routing table. Routers within an autonomous system must keep the link state database synchronized to form a consistent view of the network topology. OSPF relies on the Hello protocol, Exchange protocol and Flooding protocol to complete the interaction process of OSPF packets, and ultimately achieve synchronization of LSDB of all routers in the same routing area.

[0005] The entire working process of OSPF is composed of three interactive protocols:

[0006] (1)Hello protocol: used for discovering and maintaining OSPF neighbor relationship, periodically sent through timer. On the network, the Designed Router (DR) and Backup Designed Router (BDR) are elected, in this way, the neighbor relationship between two routers is established. The Hello packet of the five OSPF packets is interacted.

[0007] (2)Exchange protocol: after two routers establish a bidirectional connection through the adjacency protocol, their databases must be synchronized, and the synchronization process is completed through the exchange protocol. The Database Description (DD) packet of the five OSPF packets is interacted, only containing the LSA header information.

[0008] (3)Flooding protocol: in order to reduce unnecessary traffic, only some database description packets are sent by the exchange protocol, and the real link state announcement is sent through the flooding protocol. The following three of the five OSPF packets are interacted: Link State Update (LSU) containing complete LSA information, Link State Request (LSR) requesting the entire LSA information, and Link State Acknowledge (LSA) sent to ensure correct sending and receiving of LSA.

[0009] The link state awareness method currently used in the network routing protocol is mainly suitable for wired networks. Such a method mainly relies on protocol packet interaction for detecting link on-off, topology change and the like. The interaction period is 10 seconds in the (OSPFv3) protocol (RFC5340) by default, the number of confirmations is 3 times, and the link detection time is a random value between 20-30 seconds. There are generally weak real-time link detection, inability to reflect the real link state, and long re-routing time. In a large-scale network, it is easy to cause large task response delay, high data loss rate and other phenomena. SUMMARY

[0010] In order to overcome at least one of the deficiencies in the prior art, the present application provides a network routing link state real-time awareness method based on cross-layer cooperation.

[0011] In a first aspect, a network routing link state real-time awareness method based on cross-layer cooperation is provided, comprising:

[0012] The FPGA receives frame synchronization signals of multiple ports, and respectively performs edge detection on the frame synchronization signals of the multiple ports to obtain multiple detection signals; the multiple detection signals are input to an OR gate in the FPGA to obtain a combined signal; the combined signal is input to a monostable counter to keep for a set time, and then output as an interrupt signal to a CPU processor;

[0013] The FPGA synchronously samples the frame synchronization signals of the multiple ports to obtain multiple port frame synchronization state values, and maps the multiple port frame synchronization state values to a specified IO space address of the CPU processor;

[0014] After the CPU processor receives the interrupt signal, the CPU processor reads the frame synchronization state values of each port in the specified IO space address through an IO bus, as a new link on-off flag; when initializing a routing protocol, the CPU processor reads the frame synchronization state values of each port in the specified IO space address through the IO bus, as a link on-off flag when initializing the routing protocol;

[0015] If the link on-off flag of a port changes from off to on, the link on-off flag of the port is set to up, a Hello packet sending timer of the port is started, and a neighbor relationship is established by exchanging Hello information with other routers; if the link on-off flag of a port changes from on to off, the link on-off flag of the port is set to down, and all neighbors in a port neighbor list are deleted; an update of a routing table is triggered, DR and BDR of the port are both set to null, a port link state response queue is cleared, a link state response timer, a Hello packet sending timer, and a waiting timer are closed, and a Hello packet without neighbor information is sent to inform other routers that the port is disconnected, to inform other routers of network changes and trigger an update of the routing table;

[0016] Hello packet information is updated, and Hello packets are sent at a period on each connected port, and each node in the network updates a routing table according to a protocol.

[0017] In one embodiment, all neighbors in a port neighbor list are deleted, including:

[0018] A neighbor inactivity timer, a DD sending timer, and a link state request timer are closed, and LSA in a link state retransmission list, a database digest list, and a link state request list are cleared.

[0019] In one embodiment, the set time is 50 us.

[0020] In one embodiment, the method further includes:

[0021] When the CPU processor is powered on and initialized, the frame synchronization state values of each port are read in the designated IO space address through the IO bus, as the link on-off flag during power-on initialization.

[0022] In a second aspect, a network routing link state real-time sensing device based on cross-layer cooperation is provided, comprising an FPGA and a CPU processor, and the device is used to implement the network routing link state real-time sensing method based on cross-layer cooperation.

[0023] Compared with the prior art, the network routing link state real-time sensing method based on cross-layer cooperation has the following beneficial effects: in the method, the link state detection in the routing protocol not only uses Hello packet interaction in the network layer, but also uses the frame synchronization indication reported by the physical layer; the inter-satellite link state is achieved by using the active detection mode for the inter-satellite laser terminal frame synchronization state, and the real-time detection of the inter-satellite link on-off state and link quality is completed in combination with the inter-satellite link signal capture and tracking, signal processing, link quality detection and other functions, and the detection result is reported to the inter-satellite routing protocol processing function unit to trigger routing update. The method can effectively control the routing interaction overhead, and can respond in real time and perform fast re-routing when the inter-satellite link on-off changes, the satellite node abnormally fails and the like, thereby providing a real-time and accurate link state detection scheme for a wireless network communication system. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application can be better understood by reference to the following description taken in connection with the accompanying drawings, which together with the detailed description below are incorporated in this specification and form a part hereof. In the drawings:

[0025] Figure 1 A principle diagram of the network routing link state real-time sensing method based on cross-layer cooperation is shown. DETAILED DESCRIPTION

[0026] In the following, exemplary embodiments of the present application will be described with reference to the drawings. In the specification, not all the features of the actual embodiments are described for the sake of brevity and clarity. It should be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions can be made to achieve the developer's specific goals, and these decisions will vary from one implementation to another.

[0027] It should also be noted that, in order not to obscure the application with unnecessary detail, only the structures closely related to the scheme according to the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0028] It is to be understood that the application is not limited to the described embodiments on account of the description hereinbelow with reference to the drawings. Insofar as possible, the embodiments can be combined with one another, features can be replaced or borrowed between different embodiments, and one or more features can be omitted in an embodiment.

[0029] The embodiment of the application provides a network routing link state real-time sensing method based on cross-layer cooperation, which is based on FPGA (Field Programmable Gate Array) and CPU (Central Processing Unit) and is used for real-time sensing of an inter-satellite network routing link state. A laser terminal is arranged on a satellite, the laser terminal comprises a laser module and a routing module, and the FPGA and the CPU are components in the routing module. In the method, the FPGA acquires frame synchronization signals of a plurality of ports of the laser module, and further processes the signals, and finally realizes the network routing link state real-time sensing method.

[0030] Figure 1 A principle diagram of the network routing link state real-time sensing method based on cross-layer cooperation is shown, referring to Figure 1 , the method comprises the following steps.

[0031] In step S1, the FPGA receives frame synchronization signals of a plurality of ports, and respectively performs edge detection on the frame synchronization signals of the plurality of ports to obtain a plurality of detection signals. Here, the edge detection comprises detection of rising edges and falling edges, and the number of ports can be 2. The plurality of detection signals are input into an OR gate in the FPGA to obtain a combined signal. The combined signal is input into a monostable multivibrator to keep for a set time, and then is output to the CPU as an interrupt signal.

[0032] Here, the set time can be 50us, or other values.

[0033] In this step, among a plurality of signals representing link establishment states given by the laser terminal, for example, a tracking success indication, a capture success indication, a decoding synchronization indication, a frame synchronization indication and a CRC (Cyclic Redundancy Check) check, the frame synchronization indication (i.e. the frame synchronization signal) is selected as a flag for judging link continuity. The frame synchronization indication is high level, representing that the link is connected, and is low level, representing that the link is interrupted.

[0034] In step S2, the FPGA performs synchronous sampling on the frame synchronization signals of the plurality of ports to obtain a plurality of port frame synchronization state values, and maps the plurality of port frame synchronization state values to an IO space address specified by the CPU, for example, 0x00039C.

[0035] Step S3, after receiving the interrupt signal, the CPU processor reads the frame synchronization state value of each port in the designated IO space address through the IO bus, as the new link up / down flag; during the initialization of the routing protocol, the CPU processor reads the frame synchronization state value of each port in the designated IO space address through the IO bus, as the link up / down flag during the initialization of the routing protocol.

[0036] Step S4, comparing the new link up / down flag with the current link up / down flag, if the link up / down flag of a port changes from down to up, the link up / down flag of the port is set to up, the Hello packet sending timer of the port is started, and the neighbor relationship is established by exchanging Hello information with other routers; if the link up / down flag of a port changes from up to down, the link up / down flag of the port is set to down, all neighbors in the neighbor list of the port are deleted; the update of the routing table is triggered, the DR and BDR of the port are both set to null, the port link state response queue is cleared, the link state response timer, the Hello packet sending timer and the waiting timer are closed; a Hello packet without neighbor information is sent to inform other routers that the port is disconnected, so as to inform other routers of the network change and trigger the update of the routing table.

[0037] Specifically, all neighbors in the neighbor list of the port are deleted, including:

[0038] The neighbor inactivity timer, the DD sending timer and the link state request timer are closed, and the LSA in the link state retransmission list, the database digest list and the link state request list is cleared.

[0039] Step S5, the Hello packet information is updated, and the Hello packet is sent in each connected port according to the period, and each node in the network updates the routing table according to the protocol.

[0040] Further, before step S1 is performed, the frame synchronization state value of each port is read in the designated IO space address through the IO bus by the CPU processor during the power-on initialization, as the link up / down flag during the power-on initialization.

[0041] In this embodiment, the inter-satellite link state active detection is realized by using the active detection mode of the inter-satellite laser terminal, and the real-time detection of the inter-satellite link up / down state and link quality is completed by combining the inter-satellite link signal capture and tracking, signal processing, link quality detection and other functions, and the detection result is reported to the inter-satellite routing protocol processing function unit.

[0042] The inter-satellite link topology of the whole network is predicted. The inter-satellite topology of the low-orbit constellation has the characteristic of regular change. The constellation topology and routing information of different time periods can be stored in the satellite in advance or be given to the satellite by the ground. The inter-satellite routing protocol processing function unit can predict the topology state of the inter-satellite link of the whole network according to the current system time. On this basis, the inter-satellite topology and link state are updated and confirmed according to the inter-satellite link state detection result reported by the inter-satellite laser terminal or the inter-satellite microwave terminal in real time.

[0043] The local inter-satellite link period detection (within two hops) is mainly to detect the state of each group of inter-satellite links, and the purpose of the local inter-satellite link period detection is to periodically exchange the neighbor node and link state information in the local area. On the one hand, the routing exchange overhead is effectively controlled, and on the other hand, when the inter-satellite link state conversion, satellite node abnormal failure and the like occur, real-time response and fast re-routing can be performed.

[0044] The embodiment of the application further provides a network routing link state real-time sensing device based on cross-layer cooperation, comprising an FPGA and a CPU processor. The device is used to realize the network routing link state real-time sensing method based on cross-layer cooperation of the foregoing embodiment. The specific implementation functions and technical effects of each module can be referred to the foregoing embodiment.

[0045] Specifically, the CPU processor can adopt a BM3823 CPU.

[0046] The above is only various embodiments of the application, but the protection scope of the application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method for real-time perception of network routing link status based on cross-layer cooperation, characterized in that, include: The FPGA receives frame synchronization signals from multiple ports and performs edge detection on the frame synchronization signals from each port to obtain multiple detection signals. The multiple detection signals are input to an OR gate in the FPGA to obtain a combined signal; the combined signal is input to a monostable counter and held for a set time before being output to the CPU processor as an interrupt signal. The FPGA synchronously samples the frame synchronization signals of the multiple ports to obtain the frame synchronization status values ​​of the multiple ports, and maps the frame synchronization status values ​​of the multiple ports to the IO space address specified by the CPU processor. After receiving the interrupt signal, the CPU processor reads the synchronization status value of each port frame from the specified IO space address through the IO bus, and uses it as a new link connection / disconnection flag. During routing protocol initialization, the CPU processor reads the synchronization status values ​​of each port frame from the specified IO space address via the IO bus, which serve as the link connectivity flag during routing protocol initialization. Comparing the new link connectivity flag with the current link connectivity flag, if the link connectivity flag of a port changes from disconnected to connected, then the link connectivity flag of that port is set to up, the Hello packet sending timer for that port is started, and neighbor relationships are established by exchanging Hello information with other routers; if the link connectivity flag of a port changes from connected to disconnected, then the link connectivity flag of that port is set to down, all neighbors in the neighbor list of that port are deleted; a routing table update is triggered, the DR and BDR of that port are both set to empty, the link state response queue of that port is cleared, and the link state response timer, Hello packet sending timer, and wait timer are turned off; a Hello packet without neighbor information is sent to inform other routers that the port is disconnected, so as to notify other routers of network changes and trigger routing table updates; Update Hello packet information, send Hello packets periodically on each connected port, and update the routing table of each node in the network according to the protocol.

2. The method as described in claim 1, characterized in that, in, Delete all neighbors in the port's neighbor list, including: Turn off the Neighbor Inactivity Timer, DD Transmit Timer, and Link State Request Timer, and clear the LSAs from the Link State Retransmission List, Database Summary List, and Link State Request List.

3. The method as described in claim 1, characterized in that, The set time is 50us.

4. The method as described in claim 1, characterized in that, The method further includes: When the CPU processor is powered on and initialized, it reads the synchronization status value of each port frame from the specified IO space address through the IO bus, which serves as the link connectivity flag during power-on initialization.

5. A real-time network routing link status sensing device based on cross-layer cooperation, characterized in that, The device, comprising an FPGA and a CPU processor, is used to implement the real-time network routing link status awareness method based on cross-layer cooperation as described in any one of claims 1-4.

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